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Questions and Answers
What operation is used when locating a record address randomly in a direct access file?
What operation is used when locating a record address randomly in a direct access file?
- Hashing (correct)
- Indexing
- Linear search
- Sequential search
In an indexed sequential file, what does the key field determine?
In an indexed sequential file, what does the key field determine?
- The position of a record (correct)
- The type of search algorithm used
- The number of records
- The value of the record
How is the index calculated in a direct access file example using the CustomerID?
How is the index calculated in a direct access file example using the CustomerID?
- CustomerID MOD 10 (correct)
- CustomerID / 10
- CustomerID - 5
- CustomerID + 10
Which of the following statements about direct access files is true?
Which of the following statements about direct access files is true?
What is the primary advantage of using indexed sequential files?
What is the primary advantage of using indexed sequential files?
Which of the following describes sequential search?
Which of the following describes sequential search?
What is a disadvantage of using hashing in direct access files?
What is a disadvantage of using hashing in direct access files?
In the context of indexed sequential files, which of the following is true about record addresses?
In the context of indexed sequential files, which of the following is true about record addresses?
What is the primary feature of a sequential file?
What is the primary feature of a sequential file?
What was the original intention behind designing sequential files?
What was the original intention behind designing sequential files?
In the context of sequential file processing, what happens if the retrieved name is incorrect?
In the context of sequential file processing, what happens if the retrieved name is incorrect?
How does an indexed sequential file differ from a basic sequential file?
How does an indexed sequential file differ from a basic sequential file?
What is emphasized in the usage of direct indexing in indexed sequential files?
What is emphasized in the usage of direct indexing in indexed sequential files?
What primarily distinguishes logical organization from physical organization of data?
What primarily distinguishes logical organization from physical organization of data?
Which statement accurately describes a key field in a database record?
Which statement accurately describes a key field in a database record?
In which situation would a serial file be typically used?
In which situation would a serial file be typically used?
What is indicated when records are stated to be stored at different indices or locations?
What is indicated when records are stated to be stored at different indices or locations?
Which of the following best defines a database?
Which of the following best defines a database?
When searching for a record, which method allows for the quickest retrieval?
When searching for a record, which method allows for the quickest retrieval?
What must a record in a serial file maintain to ensure proper data input/output?
What must a record in a serial file maintain to ensure proper data input/output?
Which of these describes a binary file?
Which of these describes a binary file?
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Study Notes
Logical vs. Physical Organization of Data
- Logical Organization: Represents how programs access data abstractly, utilizing logical structures like linked lists.
- Physical Organization: Refers to the actual arrangement of data in memory, detailing the sequence of bits.
Definitions
- Database: A collection of related files.
- File: A collection of related records, which can be text files or binary files (including formats like graphic and word-processing).
- Record: Consists of related fields.
- Key Field: Uniquely identifies each record; a primary key contains unique values within a table.
Basics (General Idea)
- Records can be stored at various indices, requiring knowledge of their locations for retrieval.
- Options for finding a record include searching, jumping directly to a location, or a combination of both.
Serial Files
- Serial File: Contains records without a defined order; often used in transaction records (e.g., banking).
- Records are entered in chronological order, and a defined format is necessary for correct data input/output.
Sequential Files
- Records are stored sequentially based on a key field, such as names alphabetically.
- Originally designed for magnetic tape operation, retrieval follows a sequential search where each name is checked in order.
Indexed Sequential Files
- Similar to an index in a book, a file index organizes records for faster access.
- Involves sequential searching for the key field, followed by locating the desired record in a specified section.
Direct Access Files
- Records can be accessed randomly through a method called "hashing," which uses the key field's value to compute a position.
- The hashing process may lead to non-unique positions (e.g., using formulas like Index ← CustomerID MOD 10).
Direct Access vs. Sequential File
- Direct Access allows for random record retrieval, while Sequential Files require a linear search process based on order.
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